In one common type of flexible coupling device, opposing hubs are arranged on ends of two axially opposed rotatable shafts. A flexible connecting sleeve axially extends between the hubs. The hubs have an annular recess provided with a plurality of internal and external engaging elements. The connecting sleeve is provided with a plurality of engaging elements similar in size and shape to the engaging elements on the hubs. When assembled, the engaging elements of the connecting member mate with the engaging elements on the hubs to provide a path for torque transmission.
Under high torque load conditions, the engaging elements on the hubs tend to interlock with the engaging elements on the connecting sleeve. The interlocking of the engaging elements on the hubs and the engaging elements on the connecting sleeve prohibits the connecting sleeve from moving relative to the hubs. When the flexible coupling device is subjected to lighter torque loads, as are often encountered in modem centrifugal pump applications using variable frequency drives, however, the engaging elements on the hubs do not properly interlock with the engaging elements on the connecting sleeve. As a result, the engaging elements on the connecting sleeve tend to slide relative to the engaging elements on the hubs. This relative sliding motion can cause wear on the engaging elements on the connecting sleeve, which will negatively effect the operation of the flexible coupling device.
Additionally, in order to replace the connecting sleeve, the hubs must be moved away from the connecting sleeve down the length of the shaft in an axial direction. Not only does this type of replacement unnecessarily disturb the connection between the hubs and the shafts, but it is also difficult and time consuming to slide the hubs down the shaft after the flexible coupling device has been in use for a prolonged period of time due to shaft corrosion, debris, or the like.